



May 5, 1936. A. col-1N 2,039,886

DUCT

Filed Sept. 7, 1935 2 Sheets-Sheet l INVENTOR Aaron Cohn ATTORNEY Mayl5, 1936. A COHN 2,039,886

DUCT

Filed Sept. 7, 1935 2 Sheets-Sheet 2 123- y INV/EN TOR BY Aaron CohnATTORNEY Patented May 5, 1936 UNITED STATES PATENT OFFICE 15 claims.

My inventionI relates to ducts, and it relates more especially tothin-walled ducts of the kind used for conveying air, smoke, and thelike.

An object of my invention is to provide duct assemblies which may befabricated at the factory, stored or shipped without waste-space; andefllciently, sturdily, and permanently assembled on the premises Withoutthe use of tools or sealing compounds.

Another object of my invention is vto provide duct assemblies of suchsimple construction that inexperienced laymen may easily and quicklyassemble the-same.

A further object of my invention is Lto, provide.

means whereby basic stocked duct partswill supply any number of ductsizes and shapes.

With the above and other objects in view, my. invention consists of asheet metal duct comprising an enclosure assembly having locking edgesformed integrally therewith, said locking edges comprising a maleformation and a female formation; the male formation consisting of abase, a shoulder extending from said base, a tongue extending from saidshoulder, and folded back on itself to a rearwardly inclined engageableedge intermediate the fold and the shoulder; and the female formationconsisting of two spaced walls resillently conjoined at their innerends, a shoulder extending from one of said walls, and a forwardlyinclined engageable edge along one wall and intermediate said inner endand said shoulder; the channel between the walls, be-

tween said engageable edge and said shoulder', being shallower than thethickness of the folded back tongue of the male formation.

For the purpose of illustrating my invention, I have shown in theaccompanying drawings forms thereof which' are at present preferred byme, since the same have been found in practice to give satisfactory andreliable results, although it is to be understood that the variousinstrumentalities of which my invention consists can be variouslyarranged and organized and that my invention is not limited to theprecise arrangements and organizations of the instrumentallties asherein shown and described.

Referring to the drawings in which like reference characters indicatelike parts,

Figure 1 represents a perspective view of a duct embodying my invention,greatly reduced .in size.

Figure 2 represents a perspective view of duct assemblies embodying myinvention in position for storage o r shipping.

Figure 3 represents a front elevational view of a duct of modifiedconstruction embodying my invention.

Figure 4 represents a front elevational view of a duct assembly of thetype shown in Figure 3, in position for shipping or storage.

Figure 5 represents a perspective view of a duct of the stovepipe type,embodying my invention.

Figure 6 represents a longitudinal sectional view of the male and femalelocking edges embodied in my invention, in unassembled position.

Figure 'I represents a sectional view of the lockseam formed by theinterlocking of the male and female edges shown in Figure 6.

Figure 8 represents a longitudinal sectional view of male and femalelocking edges of modified construction embodied in my invention, inunassembled position.

Figure 9 represents a sectional view of the lock seam formed by theinterlocking of the male and female edges shown in Figure 8.

Figure 10 represents a longitudinal sectional view of the male andfemale locking edges of another modified construction, embodied in myinvention, in unassembled position.

Figure 11 represents a sectional view of the lock seam formed by theinterlocking of the male and female edges shown in Figure 10.

Figure 12 represents a longitudinal sectional view of the male andfemale locking edges of a further modified construction, embodied in myinvention, in unassembled position.

Figure 13 represents a sectional view of the lock seam formed by theinterlocking of the male and female edges shown in Figure 12.

Figure`14 represents a longitudinal sectional view of the male andfemale locking edges of another modified construction, embodied in myinvention, in unassembled position.

Figure 15 represents a longitudinal sectional view of the male andfemale locking edges 'shown' in Figure 14, as they appear in the firststage of they assembling or interlocking operation.

Figure 16 represents a sectional view of the lock seam formed by theinterlocking of the male and female edges shown in Figures 414 and 15.

Figure 17 represents a perspective view, partly broken away, of a ductassembly of modified construction, embodying my invention.

According to-my invention, I provide a sheet metal duct I2 having planeside panels I3 and angular comer-members I4, of any desired length andbreadth.

'Ihe longitudinal margins I5, of the panels Il, are folded into maleformations I8; and the contiguous longitudinal margins I1, of thecornerl members I6,. arefolded into coacting female ment 22. Adownwardly extending shoulder 23 is formed on the panel I6 behind theengageable edge 22, in a manner to project the tongue or male projection26, comprising the double-thickness tab 26 and the single-thicknesspanel portion 26 between the engageable edge 22 and the shoulder 23, toa plane preferably two panel thicknesses lower than the plane of thepanel I3.

In my preferred form of female formation, the corner-member margin I1 isformed of sheet metal of the same thickness as the panel I3; and isdownwardly folded back on itself a distance substantially equal to thelength of the tongue 26, to form the rounded entrance wall 26 and the'upper wall 21 of the female channel 26.

At the extreme forward end 29 of the upper wall 21 the margin I1 isfolded downward to form the front wall 36 of the female formation; andthereafteris folded rearwardly to form a lower wall 3l, parallel to theupper wall 21 and spaced therefrom a distance equal to two panelthicknesses. The lower wall 6I extends from the front wall 36 to a point32 a substantial distance to the rear of the channel entrance 26, andhas formed on the rearward` portion thereof a fourthickness platen-block33. I'his block 63 is formed by the margin I1 being folded upward fromthe point 32, and forward upon itself, spaced from the lower wall 3l adistance equal to twice its thickness, to a point 36, forming the platen36. The margin I1 is then folded downward and rearward, in contiguity tothe platen 36, as at 36, to the point 62; and then is folded downwardand forward contiguous to the fold 36 and to the lower wall 3i, andextending forward beyond the channel entrance wall 26, to the raw,terminal edge 31. This terminal edge 31 forms a forwardly projectingengageable edge or abutment which is spaced from the extreme forwardchannel wall 66 a distance equal to or greater than the length of themale double4 thickness tab 26.

' There is thus formed on the lower wall 3i a quadruple-thicknessplaten-block 33 extending generally from the vertical axis of therearward point 32 to the vertical axis of the forward point 36 andhaving the upper face 36 of the platen 36 spaced from the upper face 36of the unfolded portion of the margin I1 a distance equal to one r/anelthickness. There is thus also formed a double-thickness vestibule wall66 extending from the block 33 to the engageable edge 31 and spaced fromthe upper wall 21 a distance equal to one panel thickness. The roundedforward edge 36 of the platen 36 serves as a forwardly inclined shoulderand as an entrance wall opposed to the veitrance wall 26 and opening onthe female channel 26.

The female channel 26 is thus bounded bythe rounded entrance wall 36,the lowerv vestibule wall 66, the exposed upper face 6I of the lowerwall 3I, the extreme forward wall 36, the upper wall L 21, and the upperrounded entrance wall 26.

In operation, when the panel I3 and the corner member I6 are assembled,the male double-thickness tab 26 is rested upon the female platen 36 land preferably guided forward thereon until the rounded leading edge 2|abuts the rounded entrance wall 26 of the female channel 26. The maleformation I6 is then urged downwardly, and forwardly until the maleleading edge 2| has been guided through the female channel 26 intojuxtaposition to the forward female wall 36. In

this manner, the double-thickness male tab 26 is urged through thenormally single-thickness portion of the female channel 26, forcing thevestibule wall- 66 downward against the resilience of the conjunctiveforward wall 3 I In the continued forward stroke of the male formationI6, the double-thickness tab 26 terminating in the rearwardly inclinedengageable yedge 22 uncovers the female forwardly inclined engageableedge 31 of the vestibule wall 66, and permits the-vestibule wall 66 tospring upwardly into contiguity with the single-thickness portion 26 ofthe male formation.

In this position, as illustrated in Figure 1, the male formation I6 iscompletely and sturdily embraced by the female formation I6, the Amaleformation I6 being prevented against vertical displacement by the upperfemale wall 21, the

lower female walls 66 and 6 I, and the platen-block 33; and againstforward displacement by the forward wall 36 abutting against the maleleading edge 2l, and the entrance wall 26 abutting against the maleshoulder 23. Further, the male lformation I6 is prevented from rearwarddisplacement. by the rearwardly inclined male engageable edge 22abutting against the forwardly inclined female engageable edge 61, andby the male shoulder 23 abuttingagainst the female entrance wall 36.Furthermore, the male and female formations I6 and I6 are so congurated,and so related to each other, that there is no possibility of passage ofair through the seam of the assembled duct.

The male and female locking formations have thus been solidly andpermanently locked together, and the panel I6 has been secured to thecorner member I6.

By the' use of the novel lock-seam embodied in my invention, quantitiesof similar panels I3, each having formed on the longitudinal edges I6thereof male formations I6, may be stored or shipped together; andangular corner members I6 each having formed on the longitudinalmarginal edges I1 thereof female formations I6 may be nested togetherfor storage or shipment, all as more fully 'illustrated in Figure 2.

Moreover; if desired, panels I3-a of standard width may be provided,each having formed along one longitudinal margin I6 thereof, a maleformation I6, and along the other longitudinal margin I1-a, thereof, afemale formation I6: and a coupling-panel I3-b of similar width may beprovided, having formed along both longitudinal margins I6 thereof, maleformations I6. By this means, any desired panel ysims may be formed byinterlocking the requisite number of standard panels I3-a with astandard coupling panel I3-b.

Thus, by stocking a quantity of similar standard panels I6-a, standardcouplingpanels I3-b and comer-members I6, a merchant is enabled tofurnish his customers duct assemblies of any required size or shape.

In Figures 8 and 9 are shown a modified lockseam construction embodiedin my invention whereby the margin I of the panel I3 is folded upwardlyback upon itself to form the doublethickness tab .42, the roundedleading edge 43, and the rearwardly inclined engageable edge 44. Adownward forwardly inclined shoulder 45 is formed on the panel I3 behindthe engageable edge 44 and projects the 'bottom face .of the tongue 48,comprising the double-thickness tab 42 and the single-thickness portion41 between the engageable edge 44 and the shoulder 48, to a pianethree-panel thicknesses below the bottom face of -the panel I3. Thiscomprises the male formation.

In the female formation shown in Figures 8 and 9, the margin I1 is bentdownwardly to form the rounded entrance wall 48 to the female channel48, and is folded forwardly parallel to the unfolded portion 58 of themargin I1 and spaced therefrom a distanceequal to one panel thickness,to form the upper vestibule wall 5I. This vestibule wall 5I terminatesat the point 52, va distance fromthe entrance wall 48 equal| tov thelength of the single-thickness male portion 41. 'Ihe margin I1 is bentsharply upward at 52, preferably at right angles to the vestibule wall5I to form an engageable edge at 52; and 'is thereafter folded forwardgenerally contiguous to the unfolded portion 50, to a point 53 spacedfrom the engageable edge 52 a distance equal to the length of the maledouble-thickness tab 42, whereupon it is folded downwardly to form theforward wall 53 of the female channel 48.

The margin I1 is thereafter folded rearwardly,

to form the lower female wall 54, parallel tothe vestibule wall 5I andspaced therefrom a distance;

rested on the female platen 58 and preferably is urged forwardly untilthe male leading edge 43 abuts the entrance wall 48; whereupon thetongue 48 is urged downwardly and forwardly until the leading edge 43advancesA into proximity to the forward wall 52.4V In this manner, thelower female wall 54 is forced downwardly against the resilience of theforward wall 53, to widen the normally single-thickness portion of thefemale channel 48 to admit the double-thickness tab 42. As the tongue 48progresses forward, the doublethickness tab 42 terminating in therearwardly inclined engageable edge 44, clears the forwardly inclinedengageable edge 52 of the vestibule wall 5 I, and the lower wall 54springs upward to clamp the male single-thickness portion 41 between thelower wall 54 and the vestibule wall 5I and to encase'the doublethickness tab 42. Thus the male formation is locked against vertical orlongitudinal displacement in a manner substantially similar to that ofthe embodiment of my invention illustrated in Figures 6 and 7.

In Figures l0 and l1 are shown another modified lock-seam formationembodied in my invention, wherein the male formation I8 comprises thepanel I3 having a margin I8 folded down` wardly and rearwardly uponitself, to form the double-thickness tab 58 having a rounded forwardleading edge 58 and a rearwardly inclined engageable edge 88. Aforwardly inclined shoulder 8| is formed behind the engageable edge 80and projects the tongue 82, comprising the doublethickness tab 58, andthe single-thickness portion 83 between the engageable edge 80 and theshoulder 8|, to a plane two panel-thicknesses beneath the plane of thepanel I3.

'I'he female formation I8 comprises the margin I1 folded downwardly backupon itself to form the rounded ventrance wall 84 and the upper wall 85of the female channel 88. The wall 85 extends forward a distance equalto the length of the tongue 82, whereupon it is folded downwardly toform, the extreme forward wall 81 of the female channel 88, and then isfolded rearwardly to form the lower female wal188 parallel to the wall85 and spaced therefrom a distance equal to two panel-thicknesses. Thelower wall 88 is folded upwardly back upon itself -at a point 88substantially opposite the rounded entrance wall 84, to form thevestibule wall 18 spaced fromthe upper wall 85 a distance equal to onepanel thickness, and having a rounded entrance wall 88, and

.a terminal engageable edge 1I spaced therefrom a distance equal to thelength of the single-thickness male portion 58.

In assembling operation the male tongue 82 is urged forwardly until therounded sides of its lea-ding edge 59 engage the inner rounded sides ofthe entrance walls 84 and 88 of the female formation i8. Further advanceof the tongue 82 cams the vestibule wall downwardly against theresilience of the forward wall 81, until the leading edge 58 comes intoproximity of said forward wall 81, and the shoulder 8i abuts theentrance Wall 84. In this process, the male doublethickness tab 58terminating in the rearwardly inclined engageable edge 80, uncovers theforwardly inclined female engageable edge 1I of the vestibule wall 1I);and the vestibule wall 18 snaps upwardly into clamping position againstthe single-thickness male portion 58, thereby encasg ing the maledouble-thickness tab 58 and securely locking the male formation I8within the female formation I8.

In Figures 12 and 13 are shown another modification of the lock-seamembodied in my invention. In this'embodiment, the male formation I8comprises the panel I8 having the margin I5 folded to form the upwardlyprojecting shoulder 12, and the rearwardly projecting tongue 13, thetongue 13 being spaced from the panel I3 a distance equal to twopanel-thicknesses. The margin I5 is then folded downwardly and forwardlyupon itself as at 14, contiguous to the tongue fold13 and forming thedouble-thickness tab 15 having a rearwardly projecting rounded, leadingedge 14, and terminating in a forwardly inclined engageable edge 18.

The female formation I8 comprises the margin I1 folded downwardly toform the extreme rear wall 11 of the female channel 18; and then isfolded forwardly, parallel to the unfolded portion 19 of the margin I1,and spaced therefrom a distancey equal to two panel thickness, to formthe lower female wall 88. Said lower wall 88 extends forwardly to a'point 8|, spaced from the rear wall 11 a distance equal to the length ofthe male tongue 13. At the point 8|, the margin I1 is upwardly foldedback upon itself to form -a rounded entrance wall 8l, and a vestibulewall 82 contiguous to the lower wall 88, and terminating in therearwardly inclined engageable edge 88. The unfolded portion 19 of themargin I1 comprises an upper female wall 8l and a platen face 00.

In assembling operation the male tongue 'I8 is rested upwardly againstthe female platen 88, and urged rearwardly towards-the female formationI8 until the lower side of the roimded rearwardly projected male leadingedge Il of the tonguek 13 cams against the upper side of the rounded`forwardly projected female entrance wall 0|.

Further progress in the same direction forces the female vestibule wall82 downwardly against the resilience of the conjunctive rear wall 11until the male leading edge 1l comes into proximity to said rear wall11. As the male formation I8 completes its rearward course, the doublethickness tab 15, terminating in the forwardly inclined engageable edge1B, uncovers the vestibule wall 82.'

terminating in the rearwardly inclined engageable edge 83; therebypermitting the vestibule wall to snap upwardly into clamping positionagainst the tongue 13, and the female formation I0 completely to encasethe double-thickness tab 15, thereby locking the seam, as shownparticularly in Figure 13.

In Figures 14 to 16, inclusive, are shown another modcation of thelock-seam formation embodied in my invention. In this embodiment, themale formation comprises the margin I0 folded downwardly back uponitself to form the fold 86 and then reversely folded to form the fold81, contiguous to the ,fold 88, and projecting forward thereof to formthe tongue 88. There is thus 'Ihere is thus formed on the rearward endof the lower wall 98 a platen-block |00, having the platen |00 on theupper face thereof spaced from the plane of the upper face |81 of theunfolded portion of the margin I1, a distance equal to one panelthickness. There is also formed at the forward end of the platen |00 arounded. forwardly inclined entrance wall IOI opposed to the rearwardlyinclined entrance wall 98.

In assembling operation, the male leadingedge 98 of the male tongue 88is inserted within the entrance to the female channel 99, with therounded upper side of the leading edge 98 abutting against the lowerrounded face of the entrance wall 98, and the lower rounded side of theleading edge 98 resting on the vestibule wall |04. With these two femalepoints of contact as a bearing, the male tongue 88 is swung about itsleading edge 98. downwardly against the rounded entrance wall IOI of theplaten-block |08, operatively to force the platen block |08 and thelower wall 98 on which it bears, downwardly with respect to the formed astep 89 having a forward wall 90 and a i rearward wall 9|, defining adepth preferably greater than two panel thicknesses.

The tongue 88 is downwardly folded back on itself to form adouble-thickness tab 92 having a rounded, forwardly projecting leadingedge 93, and a rearwardly inclined, raw, engageable edge 98 intermediatethe leading edge 99 and the rearward step wall 9|.

The female formation comprises the margin I1 downwardly folded back onitself to form the npper female channel wall 95 having a roundedentrance wall 96, and extending forwardly a distance equal to the lengthof the male tongue 88. The margin I1 is thereafter folded downward ioform the forward female wall 91, and then rearward to form the lowerchannel wall 98 of the female channel 99. The lower wall 98 extendsrearwardly, parallel to the upper wall 90, and spaced therefrom adistance equal to two panel thicknesses, to a point 99 a substantialdistance to the rear of the entrance wall 96. The margin i1 isthereafter folded upwardly and forwardly upon itself to form the platen|00 parallel to the lower wall 98 and spaced therefrom a distance eoualto two panel thicknesses. The platen I 00 extends forwardly to a pointIOI spaced from the entrance wall 95 a distance equal to the depth ofthe step 89; and at IOI the margin I1 is downwardly folded back onitself to form a platenblock fold |02, extending rearwardly to the point99 and contiguous to the platen |00. The margin I1 is thereafterdownwardly folded forward on itself contiguous to the fold luz and thelowerv wall98 to form a lower platen-block fold |08 and renderne wan|04. The vestibule wan m terrninates in a raw, forwardly inclinedengageable edge |08 spaced from the forward channel wall 91 a distanceequal to the length of the male doublethi'ckness tab 82. f

engagement with the single-thickness portion |09,

of the tongue 88. At substantially the same instant the step 89, havingthe rounded forward wall 90 and the rounded rearward wall 9|, slips intolocking position between the rounded female entrance walls 90 and |0I.

The male formation I9 is thereby securely locked within the femaleformation i8; the male formation being precluded from verticaldisplacement by the vestibule wall I 04, platen |00, lower wall 98, andupper wall 95, and against longitudinal displacement by the forward wall91, engageable edge |05 and entrance walls 98 and IOI.

In Figure 3 is shown a duct of modified construction embodying myinvention. This duct comprises four segments I I0, each having a panelportion IIIand a comer-member portion I|2 formed integrally therewith.The panel portion III has formed along its longitudinal margin IIJ amale formation I6, and the corresponding cornor member portion |I2 hasformed along its longitudinal margin Ill a female formation I8. Thefemale formation is preferably formed with its forward wall contiguousto the inside surface of the panel portion III, thereby forming areinforcing corner frame on the duct. If desired, the male and femaleformations may be reversed, and the male formation I8 may be on themarginal edge III, and the female-formation I8 on the marginal edge III.

By this means it is possible to ship or store a duct assembly of myinvention in one nested package es illustrated in Figure 4.

I8, operatively to interlock into a'permanent loclr-v seam when thestove pipe is assembled. 'I'he lockseam may be any one of thoseillustrated in Figures 6 to 16 inclusive.

In Figure i1 is shown another duct assembly of modified constructionembodying my invention. In this assembly, the panels I3 have formed onthe transverse margins i2() of one end thereof, male formations; and onthe transverse margins i2i of the opposed ends thereof, femaleformations IB, thereby enabling successive rudimental duct assembliesi212 to be joined together into one complete whole I23.

It will be seen that by the use of my novel invention it is possible fora manufacturer to fabricate large quantities of duct assemblies withoutanxiety as to undue storage space or high shipping rates occasioned bygreat bulk due to waste space. Moreover, by my novel invention it ispossible for the layman to order shipped to him any desired size of ductassembly, and assemble the same by hand efficiently and in a modicum oftime. Furthermore, the lock-seam embodied in my invention is of suchconstruction that it is impossible to disengage the male and femalelocking edges thereof without intentionally prying the seam open,thereby ensuring a permanent construction to the duct of my novelinvention.

I am aware that the invention may be embodied in other specific formsWithout departing from the spirit or essential attributes thereof, and Itherefore desire the present embodiments to be considered in allrespects .es illustrative and not restrictive, reference being had tothe appended claims rather than to the foregoing description to indicatethe scope of the invention.

Having thus described my invention, what I hereby claim as new anddesire to secure by Letters Patent is:

1. A lock-seam comprising a male locking margin and a female lockingmargin: said 'male lock.- ing margin being reversely lfolded at itsleading edge, said fold terminating in an abutment contacting theunfolded portion of said locking margin throughout its length; and saidfemale locking margin comprising spaced Walls resiliently conjoined atone end thereof and dening a channel, one of said walls being inwardlyfolded in contacting relation to itself, said fold terminating in anabutment; said female abutment being adapted to abut against said maleabutment in locking engagement therewith when said lockseam isassembled.

2. A lock-seam comprising a male locking niargin and a female lockingmargin; said male locking margin being reversely folded at its leadingedge, said fold terminating in a rearwardly projecting abutmentcontacting the unfolded portion of said locking margin throughout itslength; and said female locking margin comprising spaced wallsresiliently conjoined at one end thereof and defining a channel, one ofsaid walls being inwardly folded in contacting relation to itself, saidfold terminating in a forwardly projecting abutment; said femaleabutment being adapted to abut against said male abutment in lockingengagement therewith when said lock-seam is assembled.

3. A lock-seam comprising a male locking margin and a female lockingmargin; said male locking margin being reversely folded at its leadingedge, said fold terminating in a rearwardly projecting abutmentcontacting the unfolded portion of said locking margin throughout itslength; and said female locking margin comprising spaced wallsresiliently conjoined at one end thereof and defining a channel, one ofsaid walls being inwardly folded in contacting relation to itself, saidfold terminating in a forwardly projecting f abutment; said femaleabutment being adapted to abut against said male abutment in lockingengagement therewith when said lock-seam is assembled; said female wallsrearward of said female abutment being spaced less than the thickness ofsaid male margin forward of the abutment thereof.'

4. A duct comprising an enclosure assembly having a 'male locking marginand a female locking margin; said male locking margin being reverselyfolded at its leading edge, said fold terminating in an abutmentcontacting the unfolded portion of said locking margin `throughout: itslength; and said female locking margin comprising spaced wallsresiliently conjoined at one end thereof and defining a channel, one ofsaid walls being inwardly folded in contacting relation to itself, saidfold terminatingv in an abutment; said female abutment being adapted toabut against said male abutment in locking engagement therewith whensaid enclosure is assembled.

5. A duct comprising an enclosure assembly having a male locking marginand a female locking margin; said male locking margin being reverselyfolded at its leading edge, said fold terminating in a rearwardlyprojecting abutment contacting the unfolded portion of said lockingmargin throughout its length; and said female locking margin comprisingspaced walls resiliently conjoined at one end thereof and defining achannel, one of said walls being inwardly folded in contacting relationto itself, said fold terminating in a forwardly projecting abutment;said female abutment being adapted to abut against said male abutment inlocking engagement therewith when said enclosure is assembled; saidfemale walls rearward of said female abutment being spaced less than thethickness of said male margin for ward cf the abutment thereof.

6. A lock-seam comprising a male locking margin and a female lockingmargin; said male margin comprising a base, a shoulder extending fromsaid base, a male projection extending from said. shoulder and reverselyfolded at its leading edge, said fold terminating in a rearwardlyprojecting abutment adjacent the unfolded portion of said maleprojection; and said female margin cornprising spaced walls resilientlyconjoined at their forward ends and defining a channel, one of saidwalls being inwardly folded contiguous to itself to form amultiple-thickness portion, said multiple-thickness portion extendingrearward of said. female channel, and folded into a male-base supportingplaten terminating forwardly in a shoulder adapted to abut said maleshoulder in locking engagement therewith when said lock-seam isassembled, and the forward end of said multiple-thickness portionterminating in a forwardly projecting abutment adapted to abut againstsaid male abutment in locking engagement therewith when said lock-seamis assembled.

'1. A lock-seam comprising a male locking margin and a female lockingmargin; said male margin comprising a base, a rearwardly projectingshoulder extending from said base, a male projection extending from saidshoulder and having a leading edge, a rearwardly projecting abutmentintermediate said leading edge and said shoulder, said male projectionbetween said leading edge and said abutment being substantially thickerthan said projection immediately behind said abutment; and said femalemargin comprising spaced walls resiliently conjoined at their forwardends and defining a channel, one of said walls being inwardly foldedcontiguous to itself to form a multiple-thickness portion, saidmultiple-thickness portion being folded into a forwardly projectingshoulder adapted to abut said male shoulder in locking engagementtherewith when said lock-seam is assembled, and the forward end of saidmultiple-thickness portion terminating in aq forwardly projectingabutment adapted to abut against said male abutment in lockingengagement therewith when said lockseam is assembled; said female wallsrearward of said female abutment being spaced less than the substantialthickness of said male projection forward of the abutment thereof.

8. A lock-seam comprising a male locking mar- I gin and a female lockingmargin; said male margin comprising a base, a.rearwardly projectingshoulder extending from said base. a male projection extending from saidshoulder and having a leading edge, a rearwardly projecting abutmentintermediate said leading edge and said shoulder; and said female margincomprising spaced walls resiliently conjoined at their forward ends anddening a channel, one of said walls being inwardly folded contiguous toitself to form a multiple-thickness portion, said multiple-thicknessportion extending rearward of said female channel, and folded into amale-base supporting platen terminating forwardly in a shoulder adaptedto abut said maleshoulder in locking engagement therewith when saidlock-seam is assembled, and the forward end of said multiplethicknessportion terminating in a forwardly projecting abutment adapted to abutagainst said male abutment in locking engagement therewith when saidlock-seam is assembled.

9. A lock-seam comprising a male locking margin and a female lockingmargin; said male margin comprising a base, a rearwardly projectingshoulder extending from said base, and having a thickness substantiallygreater than said base, a male projection extending from said shoulderand having a leading edge, a rearwardly projecting abutment intermediatesaid leading edge and said shoulder; and said female margin comprisingspaced walls resiliently conjoined at their forward ends and defining achannel, one of said walls being inwardly folded contiguous to itself toform a multiple-thickness portion, said multiple-thickness portion beingfolded into a forwardly projecting shoulder adapted to abut said maleshoulder in locking engagement therewith when said lock-seam isassembled, and the forward end of said multiple-thickness portionterminating in a forwardly projecting abutment adapted to abut againstsaid male abutment in locking engagement therewith when said lockseam isassembled.

10. A lock-seam comprising a male locking margin and a female lockingmargin; said male margin comprising a base, a shoulder extending fromsaid base, a male projection extending from said shoulder and reverselyfolded at its leading edge, said fold terminating in a rearwardlyprojecting abutment adjacent the unfolded portion of said maleprojection; and said female margin comprising spaced walls resilientlyconjoined at their 'forward ends and defining achannel, one

of said walls being inwardly folded contiguous to itself to form amultiple-thickness portion, said multiple-thickness portion being foldedinto a forwardly projecting shoulder adapted to abut said male shoulderin locking engagement therewith when said lock-seam is assembled, andthe forward end of said multiple-thickness portion terminating in aforwardly projecting abutment adapted to abut against said male abutmentin locking engagement therewith when said lockseam is assembled.

11. A duct comprising an enclosure assembly having a male locking marginand a female locking margin; said male locking margin comprising a base,a shoulder extending from said base, a male projection extending fromsaid shoulder and having a rearwardly projecting leading edge, aforwardly projecting abutment intermediate said leading edge and saidshoulder; and said female margin comprising spaced walls resilientlyconjoined at their rearward ends and defining a channel, one of saidwalls being inwardly folded in contacting relation to itself, said foldterminating in a rearwardly projecting abutment; said female abutmentbeing adapted to abut against said male abutment in locking engagementtherewith when said enclosure is assembled.

12. A lock seam comprising a male locking margin and a female lockingmargin; said male margin comprising a base, a shoulder extending fromsaid base, a male projection extending from said shoulder and having arearwardly projecting leading edge. said male projection being reverselyfolded at its leading edge, said fold terminating in a forwardlyprojecting abutment adjacent the unfolded portion of said maleprojection; and said female margin comprising spaced walls resilientlyconjoined at their rearward ends and defining a channel, one of saidwalls being inwardly folded in contacting relation to itself, said foldterminating in a. rearwardly projecting abutment; said female abutmentbeing adapted to abut against said male abutment in locking engagementtherewith when said lock seam is assembled.

13. A duct comprising panels and corner members, locking margins formedon said panels and corner members substantially throughout their length,said margins comprising a male formation and a female formation; saidmale formation being reversely folded at its leading edge, said foldterminating in an abutment; and said female formation comprising spacedwalls resiliently conjoined at one end thereof and defining a channel,one of said walls being inwardly folded in contacting relation toitself, said fold terminating in an abutment; said female abutment beingadapted to abut against said male abutment in locking engagementtherewith when said duct is assembled.

14. A duct comprising a panel having a longitudinally disposed malelocking margin, and a longitudinally disposed female locking margin, oneof said locking margins being disposed at an angle to said panel; aplurality of adjacent oil'- set panels, one of said offset panels havinga female locking margin adapted to be interlocked with said male lockingmargin, and another of said on'set panels having a male locking marginadapted to be interlocked with said first-mentioned female lockingmargin; each of said male locking margins being reversely folded at itsleading edge, said fold terminating in an abutment; and each of saidfemale locking margins comprising spaced walls resiliently conjoined atone end thereof and defining a channel, one of said walls being inwardlyfolded in contacting relation to itself, said fold terminating in anabutment; said lfemale abutment being adapted to abut against said maleabutment in locking engagement therewith when said duct is assembled.

15. A duct comprising a plurality of longitudinally interlockedsections; one of said sections having a transversely disposed malelocking margin adapted to interlock with a juxtaposed transverselydisposed female locking margin on the next adjacent section; said malelocking margin being reversely folded at its leading edge, said foldterminating in a rearwardly projecting abutment contacting the unfoldedportion of said margin; and said female locking margin comprising spacedwalls resiliently conjoined at one end thereof and defining a channel,one of said walls being inwardly folded in contactingl lrelation toitself, said fold terminating in a formale margin where the fold thereofcontacts 10 the unfolded portion thereof.

AARON COHN.

